This invention relates to a process for cyanothylation of hydroxy compounds. More particularly, this invention relates to the production of beta-cyanoethyl capped hydroxy compounds that are essentially free of polyacrylonitrile by-products.
The production of beta-cyanoethyl capped hydroxy compounds by cyanoethylation is well known in the art and involves the addition reaction of an alcohol and acrylonitrile to form the corresponding beta-cyanoethyl capped alcohol (i.e., oxy nitrile) as exemplified by the following equation: EQU ROH + H.sub.2 C = CHCN .fwdarw. ROCH.sub.2 CH.sub.2 CN
wherein R is an organic radical. The reaction proceeds rapidly and yields as high as about 97 percent can be obtained with certain alcohols. Strong bases, such as alkali metal alcoholates, oxides and hydroxides are the most common catalysts for effecting cyanoethylation (British Patent 544,421), although anion-exchange resins (U.S. Pat. No. 2,658,070) are also satisfactory catalysts.
However, one of the most serious drawbacks to cyanoethylation of alcohols in the presence of strong bases is the varying amounts of polyacrylonitrile byproduct formed as reported by J. Cason et al., J. Org. Chem., 37, 1972 page 2577 (footnote No. 15) and M. J. Astle et al, Industrial and Engineering Chemistry, 44, 1952, page 2872. In addition to homopolymers of acrylonitrile, block copolymers of acrylonitrile may also be formed when strongly basic catalysts are used as reported in U.S. Pat. No. 3,544,615. In certain utility applications the presence of polyacrylonitrile or its block copolymers in the desired oxy nitrile product may be of no consequence. However, polyacrylonitrile or its block copolymers are poisons for many nobel metal catalysts such as nickel, palladium, platinum and the like. Thus, when it is desired to hydrogenate the oxy nitrile product to form primary amines the presence of polyacrylonitrile by-product is very troublesome. Similarly, the production of silicon-oxyalkylene nitrile compounds by platinum catalyzed hydrosilylation of a terminal olefin of an oxyalkylene nitrile (produced by cyanoethylation) in the presence of polyacrylonitrile contaminates proceeds slowly and incompletely. The problem is further aggravated in that prolonged contact of the silicon-oxyalkylene nitrile product with the poisoned platinum catalyst causes retrocyanoethylation and much of the acrylonitrile formed under these conditions will in turn form further polyacrylonitrile.
While the bulk of the polyacrylonitrile by-product cannot generally be successfully removed from a cyanoethylated alcohol by filtration or treatment with carbon black, it has been taught (U.S. Pat. No. 3,544,615) that polyacrylonitrile can be removed from certain cyanoethylated alcohols by employing a solvent that is miscible with the cyanoethylated product and immiscible with the polyacrylonitrile. However, such a purification process is an additional procedural step that must be carried out on the cyanoethylated alcohol product.
Thus, there is a clear need in the art for a cyanoethylated process that will produce beta-cyanoethyl capped hydroxy compound products that are already essentially free of polyacrylonitrile by-products, and which will eliminate the need for such purification procedures.